lkml.org 
[lkml]   [2020]   [Jun]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: arm64/acpi: NULL dereference reports from UBSAN at boot
On Wed, May 27, 2020 at 02:41:04PM +0100, Lorenzo Pieralisi wrote:
> On Tue, May 26, 2020 at 09:21:57PM +0100, Will Deacon wrote:
> > Hi Lorenzo, Hanjun, [+Nick]
> >
> > On Thu, May 21, 2020 at 06:37:38PM +0100, Lorenzo Pieralisi wrote:
> > > On Thu, May 21, 2020 at 11:09:53AM +0100, Will Deacon wrote:
> > > > Hi folks,
> > > >
> > > > I just tried booting the arm64 for-kernelci branch under QEMU (version
> > > > 4.2.50 (v4.2.0-779-g4354edb6dcc7)) with UBSAN enabled, and I see a
> > > > couple of NULL pointer dereferences reported at boot. I think they're
> > > > both GIC related (log below). I don't see a panic with UBSAN disabled,
> > > > so something's fishy here.
> > >
> > > May I ask you the QEMU command line please - just to make sure I can
> > > replicate it.
> >
> > As it turns out, I'm only able to reproduce this when building with Clang,
> > but I don't know whether that's because GCC is missing something of Clang
> > is signalling a false positive. You also don't need all of those whacky
> > fuzzing options enabled.
> >
> > Anyway, to reproduce:
> >
> > $ git checkout for-next/kernelci
> > $ make ARCH=arm64 CC=clang CROSS_COMPILE=aarch64-linux-gnu- defconfig
> > <then do a menuconfig and enable UBSAN>
> > $ make ARCH=arm64 CC=clang CROSS_COMPILE=aarch64-linux-gnu- Image
> >
> > I throw that at QEMU using:
> >
> > qemu-system-aarch64 -M virt -machine virtualization=true \
> > -machine virt,gic-version=3 \
> > -cpu max,sve=off -smp 2 -m 4096 \
> > -drive if=pflash,format=raw,file=efi.img,readonly \
> > -drive if=pflash,format=raw,file=varstore.img \
> > -drive if=virtio,format=raw,file=disk.img \
> > -device virtio-scsi-pci,id=scsi0 \
> > -device virtio-rng-pci \
> > -device virtio-net-pci,netdev=net0 \
> > -netdev user,id=net0,hostfwd=tcp::8222-:22 \
> > -nographic \
> > -kernel ~/work/linux/arch/arm64/boot/Image \
> > -append "earlycon root=/dev/vda2"
> >
> > I built QEMU a while ago according to:
> >
> > https://mirrors.edge.kernel.org/pub/linux/kernel/people/will/docs/qemu/qemu-arm64-howto.html
> >
> > and its version 4.2.50 (v4.2.0-779-g4354edb6dcc7).
> >
> > My clang is version 11.0.1.
>
> Thanks a lot Will.
>
> I *think* I was right - it is the ACPI_OFFSET() macro:
>
> #define ACPI_OFFSET(d, f) ACPI_PTR_DIFF (&(((d *) 0)->f), (void *) 0)
>
> that triggers the warnings (I suspected it because at least in one of
> the warnings I could not see any dereference of any dynamically
> allocated data).

Cheers, Lorenzo.

> Now on what to do with it - thoughts welcome.

Nick -- any idea what to do about the above? The '#define' pasted by
Lorenzo is causing a couple of spurious UBSAN splats when compiling with
clang 11.

Cheers,

Will

\
 
 \ /
  Last update: 2020-06-01 09:06    [W:0.090 / U:12.168 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site